A simple approach to calculate active power of electrosurgical units

Abstract

Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods: This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables -frequency domain vectors -obtained through Discrete Fourier Transform (DFT) applied on time-sampled voltage and current vectors. Results: Comparative results between simulations and a practical experiment are presented -all being in accordance with the requirements of the applicable industry standards. Conclusion: An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.

Low cost system to measure active power in electrosurgical units

“…In addition, the readings v(t) and i(t) were applied to a knowing ESU active power calculation methodology, presented by Monteiro (Monteiro et al, 2016), and the results are presented in column P approach . The absolute error between this calculation and the P comp are presented in App Error column.…”

“…2017 December;33(4): 313-323 1989). From the end of the 1990s, efforts were made to determine the power through computational tools (Fritz and Schall, 2014;Monteiro et al, 2016;Visser et al, 1991;Zhou et al, 2014) and the new topologies development, where new control techniques could be employed (Friedrichs et al, 2012;Jensen and Maksimovic, 2017;Schneider and Abatti, 2005;Wurzer et al, 1997). Unfortunately, these techniques are either inefficient or have a high implementation cost, which makes their commercial application not practical.…”